Overview of O-ring marking options.

To ensure fast visual identification of materials during production and inspection, O-rings may be marked with coloured dots using food-safe, non-contaminating inks. These dot markings are applied without affecting the seal’s performance or dimensional tolerance. Each colour corresponds to a specific elastomer compound—commonly, blue for NBR, red for FKM (Viton®), green for EPDM, and white for silicone—though exact colour codes can vary between manufacturers. Customers are advised to confirm markings against supplied documentation.

In many applications, O-rings are marked with a single coloured dot on the sidewall of the seal to allow quick material identification without compromising sealing surfaces. These side dot markings use inert, non-migrating inks that are compatible with most sealing environments. Typical usage includes blue for NBR, green for EPDM, red for FKM (Viton®), and white for silicone, though marking systems may vary by supplier. Side dot marking is ideal for cleanroom packing, automated inspection, or when multiple compounds are used in a single assembly line.

For enhanced traceability and compound verification, some O-rings are marked with four coloured dots on the side or outer diameter. This multi-dot system allows for more granular identification of material type, hardness (durometer), curing system, or manufacturing batch. The combination of colours—typically drawn from a fixed internal code—ensures clear differentiation even in environments where single-colour marking may be ambiguous. Inks are non-conductive, chemically stable, and resistant to smearing, ensuring markings remain intact during handling and storage. This system is especially valuable in regulated sectors such as aerospace, medical, and food processing.

In precision-critical industries, four-colour side marking provides a robust method for identifying O-ring specifications at a glance. Applied to the sidewall of the O-ring, this marking system uses four distinct coloured dots to encode information such as material compound, durometer, curing process, and production batch. The inks used are chemically inert, non-transferable, and designed to withstand standard cleaning and assembly procedures. This method enhances traceability and reduces the risk of misapplication, particularly when multiple elastomer grades are used in a single assembly or facility. Colour sequences follow internal or customer-specific coding standards.